Thanks for the reply. As I am not very computer savvy I need to go in smaller steps. Do I the download straight to Calibre, and if so how do I do this so that I don't go into ADE first?

You're welcome the download, from your browser, should bring you directly to ADE if they're DRM-ed; then you can add the file from finder/explorer/... to calibre or from within calibre (import). If they aren't, you will find the files in the download directory, and from there you can add them to calibre.